Satern has caliber-specific and two (?) universal. Having not looked at plastic, I don't know if they are available caliber-specific. If they are (which I assume they are) not that could be a benefit though it's more of a preference in my opinion. What is a naturual advantage is there are no concerns with static that plastics have. Though to reduce or eliminate static with plastics they can be wiped with a dryer sheet. I said all that to say that there's not much advantage if any. But, I have some on order. I simply prefer metal over plastic.

I use the Frankford Arsenal Powder Funnel Kit. It has 1 main funnel, and multiple nozzles for each caliber. I like it a lot. If a plastic funnel starts getting clingy from static, I wad up a drier sheet and pull it through the funnel and wipe off the funnel. It works very well.

I've got an RCBS funnel w/ 3-4" drop tube, I've got a Hornady red plastic funnel and I've got the pan w/ the funnel end. They all did have static issues early on but that eventually goes away, Chad gave the solution if it's not manageable or bugs you.

I don't use the pan to drop into the case I use either the RCBS or the Hornady depending on if I am packing powder in with the drop tube or not. I've thought about buying the Saturn but the plastic ones work just fine.